A copying machine includes a reading device of an image.
According to a size detecting device provided in the copying machine in advance, or an input of a user, the reading device acquires document size information. The reading device reads an image of a document.
In the related art, the reading device includes a surface area within a glass plate as a reading target. The surface area is designated by a movable range of a reading unit such as a carriage.
In the reading device, the premise is that the position and the size of the document match the surface area.
However, the position of the document may not match the designated position. Otherwise, a user may input incorrect document size information.
The reading device cannot accurately perform reading.
The read image deviates from a desired image. In a document having an unfixed size, the reading for an accurate document size cannot be performed.